docs: def has_been_completed_by(poll, user):
      """ This will return a boolean indicating if the passed user has already voted in the given
          poll.
  
      Usage::
          {% if poll|has_been_completed_by:user %}...{% endif %}
  
      """
      user_votes = TopicPollVote.objects.filter(
          poll_option__poll=poll)
      if user.is_anonymous:
          forum_key = get_anonymous_user_forum_key(user)
          user_votes = user_votes.filter(anonymous_key=forum_key) if forum_key \
              else user_votes.none()
      else:
          user_votes = user_votes.filter(voter=user)
      return user_votes.exists()